Method and machine for making pipe



May 9, 1939. A. P. KNAPP METHOD AND MACHINE FOR MAKING" PIPE Filed Dec. 17, l936 2 Shee tsSheet 1 y 1939- v A. P. KNAPP v2,157,938

METHOD AND MACHINE FOR MAKING PIPE Filed Dec. 17, 1936 2 Sheets-Sheet 2 nventor, Alfred P. Knapp, e/QM- 7 Attorney Patented May 9, 1939 UNITED STATES PATENT OFFICE The Andrew:

Company, Inc., Long Island City, N. Y., a corporation of New York Application December 17, 1936, Serial No. 116,284

8 Claims.

This invention is a die of the core and bridge type for manufacturing pipe of soft metal by the extrusion process, and also an improvement in the process.

, The extrusion process has been practiced for more than a hundred years but today the pipe produced is not of the uniformity required by the exacting conditions in many fields where use is made of lead pipe.

19 The principal object of this invention is to produce pipefree from cleavage planes, lamination and scoring which reduce the strength and leave seams that are liable to open under high pressure. Another object is to insure uniform wall thickness of the pipe. Another object is to increase the density or the metal strength of the lead.

In the accompanying two sheets of drawings which form a part of this specification, a machine is shown with a die drawn to scale for pipe of 20 two inch inside diameter, in which,

Figure 1 is an elevation partly in section of a hydraulic press embodying this invention.

Fig. 2 is a section through the extrusion die on the line 11-11 of Figs. 3 and 4.

Fig. 3 is a view of the die from underneath.

Fig. 4 is a section through the die on the line IV-IV of Fig. 2.

The press for practicing the process comprise a reservoir I 0 mounted on a plunger l I which so is the carrier of the reservoir and is elevated by hydraulic pressure applied in the base l2 of the press. The reservoir is filled with molten lead or an alloy of lead or other fusible metallic material in a molten state from which the pipe is to be formed. An elevated cross-head I3 is rigidly supported from the base by bolts M. A hollow fixed ram I5 is carried by the cross-head. The ram fits as a piston into the reservoir. The upper surface of the metal is exposed and the reservoir is free from obstruction. It is to be observed that there is means for effecting relative movement between the carrier of the reservoir and the ram which as shown is means for elevating the plunger H.

A die is fitted into the end of the ram. This is formed in two parts an exterior part with an extrusion orifice It to define the exterior size of the pipe and a depending flange l'l. Into this is fitted a sleeve l8 with bridges I! which supports a core 20 that determines the inside diameter of the pipe.

Molten lead or alloy should be poured at a temperature of approximately 800 or 900 Fahr. Extrusion should be delayed until the metal is no longer molten but is still hot and plastic. The

(Cl. 207l'l) reservoir should be heated by a flame. The speed of extrusion is principally determined by the size of the pipe and the temperature. This is current practice in the treatment of the metal.

The bridge-type of die has been used successfully only for small tubing.

For all sizes of pipe above three-eights of an inch it has been customary to attach the core to the bottom of the cylinder.

The pipe produced by the die here under dis- 1 cussion is what is called in the trade service pipe, by which is meant pipe of a size, wall thickness and other characteristics such as fits it for use under pressures demanded today of pipe in service where capacity for sustaining pressure is 1 requisite. By way of illustration it refers to pipe conducting water from mains into buildings and pipe that is used in chemical plants where high pressures and resistances to acids and high tem peratures are demanded. go

The die herein disclosed comprises a chamber which has an opening for the introduction of metal and a smaller opening for its extrusion. The core is attached to the sides of the die by bridges'of substantial dimension so as to hold the a core and die together rigidly. The bridges are tapered to a sharp edge. The orifice for the introduction of metal is but slightly restricted by the core and the bridge and the orifice for extrusion is restricted by enlargement of the di- 3. ameter of the core and by the walls of the die being drawn in toward the core. Thus there is free ingress and relatively limited egress of the metal. At the orifice of extrusion sharp shoulders are formed on the core and the wall of the a die to retard the metal.

It will be observed that there is a very considerable distance between the sharp edge of the bridges and the extrusion aperture of the die.

In the die illustrated, which is stated as intended 4 to produce pipe of an interior diameter of two inches, the distance between the sharp edge of the bridges and the point of extrusion is about 2% inches. This I have found in practice, with the die illustrated, will allow ample time, at normal speed of operation and under the pressures and temperatures maintained in making such pipe, to insure that the metal becomes thoroughly coalesced before it reaches the extrusion aperture of the die.

This I have heretofore expressed by the statement that the sharp edge of the bridge is substantially removed from the point of extrusion.

The general conformation of the chamber within the die through which the metal passes, the u 7 the metal will not certainly coalesce after passing the bridges.

The general conformation of the chamber through which the metal passes in the die and its capacity are of importance. The metal in the die is at all times under the pressure which causes the extrusion and is materially increased before extrusion occurs, as compared with the pressure required to introduce the metal into the die. The metal is forced across the flow at the point of extrusion and is there retarded and constrained by the shoulders on the die wall and on the core 20 at the extrusion orifice. Thus a uniform high pressure is insured throughout the chamber and at the point of extrusion, once extrusion begins.

The capacity of the chamber relatively to the rate of discharge should be large so that after passing the bridges the metal will be held under pressure long enough to coalesce before it reaches the point where it is extruded.

As shown, the capacity of this chamber between the bridges and the point of extrusion is sufficient to provide enough metal for a length of pipe of in times its diameter or more. This chamber may be designated as a coalescence chamber. In it the material is at all times during extrusion subjected to pressure which is required to exude the pipe. In this coalescence chamber the lead is forced to form a homogeneous mass prior to extrusion. The bond between the separate streams flowing past the bridges is found on test to be as strong as the rest of the wall of the pipe.

The method of extrusion, as practiced with the aid of the die disclosed, adds to the method of the old art holding the metal under pressure and uniform temperature while passing through the substantial distance within the die from the bridges to the point of extrusion.

A particular die which has been used is made up as follows: The outside portion of the die is an alloy of forged steel having a three and onehalf per cent nickel content. The core portion of the die including the core and bridge arms is of Swedish oil hardened tool steel. Any other metal or alloy having sufilcient strength would be acceptable. The die is illustrated in the drawings which are to scale but not full size. The upper cylindrical end of the core is about two inches in diameter which determines the bore of the pipe. The die is about six inches in height and six and one-half inches in diameter across the base. Either of these dimensions may be altered. The height to which the core rises above the outer walls of the die is of importance only because the top of the core acts as a support for the pipe. It should be substantial.

The thickness of the wall of the pipe produced is accurate throughout to a thousandth of an inch. This is because of the impossibility of relative movement between the core and the walls of the die at the point of extrusion.

The pipe is free from laminations. This is due in part to the fact that the core extends only a few inches, in the particular die mentioned about three and one-half inches, beyond the bridges. In the usual method of manufacture the core is approximately two or three feet in length, because of which lead adheres to it during production of the pipe and is impressed in fresh lead during extrusion, thus forming a double layer. Freedom from lamination is also in part due to the fact that no part of the core is in the reservoir making it possible to have access to and to compress the surface of the lead in the reservoir, whereby formation of a spongy surface, which is familiar in treating lead or like material, is avoided.

The pipe is absolutely free from scorings, pits and like irregularities. This is because the portions of the die which determine formation of the pipe are protected and when constructed for a certain size of pipe require no alteration.

To change the size of the pipe requires only the removal of a die from the ram and the substitution of a new one. Under present practice the set-up of the press for any given size of pipe may occupy more time than is available for production.

In the manufacture of pipe with this die the human element is largely eliminated.

When manufacturing pipe from tellurium lead by the use of this invention the work-hardening features of this alloy'are brought into play so that the resulting product has greater strength than pipe manufactured by the extrusion process now in general use.

I claim:

1. A die for the manufacture of service pipe of soft metal, comprising a core rigidly mounted thereon and a coalescence chamber through which the metal passes under pressure to the point of extrusion, the metal being forced to form a homogeneous mass therein prior to extrusion.

2. A die for the manufacture of service pipe of soft metal by the extrusion process, comprising a chamber through which the metal is forced under pressure, the chamber having an inlet and at the point of extrusion a relatively small outlet, a core rigidly mounted at a point substantially removed from the outlet, and means within the chamber for retarding and changing the direction of the flow, the metal thus being forced to form a homogeneous mass prior to extrusion.

3. A die for the manufacture of service pipe of soft metal by the extrusion process, comprising a coalescence chamber, wherein the lead is forced to form a homogeneous mass prior to extrusion, a core rigidly mounted by bridges spaced substantially away from the extrusion point, the chamber having an inlet and at the point of extrusion a relatively small outlet, and retarding shoulders immediately adjacent to the point of extrusion.

4. The process of forming service pipe of soft metal which consists in forcing the metal under uniform pressure past a rigidly mounted core, retaining the metal under pressure to insure coalescence into a homogeneous mass, and extruding the pipe.

5. The process of forming service pipe of soft metal of a homogeneous wall of uniform thickness which consists in forcing the metal under uniform pressure past a core rigidly mounted on bridges, retaining the metal under pressure to insure coalescence into a homogeneous mass, and extruding the pipe.

6. A die for the manufacture of service pipe of soft metal consisting of an exterior part with an extrusion orifice to define the exterior size of the pipe and a depending flange, and an interior part fitting into the exterior part and consisting of a sleeve with knifeedge bridges which support a core that determines the inside diameter of the pipe, the construction being such that, a coalescence chamber is formed between the knife edges of the bridges and the extrusion orifice of sufficient size for the metal forced past the bridges to form a homogeneous mass therein prior to extrusion.

7. A die for the manufacture of service pipe of soft metal consisting of an exteriorpart with an extrusion orifice having retarding shoulders to define the exterior size of the pipe and a depending flange, and an interior part fitting into the exterior part and consisting of a sleeve with knifeedge bridges which support a core having retarding shoulders that determines the inside diameter of the pipe, the construction being such that a coalescence chamber is formed between the knifeedges of the bridges and the extrusion orifice of suflicient size for the metal forced past the bridges to form a homogeneous mass therein prior to extrusion.

8. A die for the manufacture of extruded pipe of soft metal, comprising an open-ended metal receiving chamber, and a core extending into the exit end of said chamber to define and restrict the exit area and being rigidly supported therein by bridge supports connecting the core only at its rear end to the chamber wall, the internal free space beyond said bridge supports being suflicient to accommodate enough metal to form a length of pipe of the order of five times the diameter or more and the depth of said space being substantial in relation to the width, whereby coalescence of the metal arriving under the extrusion pressure beyond the bridge supports is ensured and also uniformity and homogeneity of the extruded pipe.

- ALFRED P. KNAPP. 

